1. Field of the Invention
The present invention pertains to an apparatus for assembling and installing pipe in a well. More particularly, the present invention pertains to a pipe running tool that can rotate at high speed, and selectively grip pipe either internally or externally. More particularly still, the present invention pertains to a pipe running tool that can be quickly and easily converted between internal and external pipe gripping simply by changing out modular components.
2. Brief Description of the Prior Art
Efficiency in connection with oil and gas operations, especially in terms of drilling rate, has been addressed with great earnest for many years. However, drilling rate is not the only variable affecting operational costs; pipe string assembly and installation rate typically has about the same cost-effect as drilling rate. The present invention addresses an increase in efficiency of such pipe string assembly and installation operations (and a resulting decrease in costs associated with such operations) without sacrificing safety concerns.
Once a well has been drilled to a desired depth, large diameter and relatively heavy pipe known as “casing” is frequently installed in the well. During installation in a well, casing is typically inserted into the pre-drilled well bore in a number of separate sections of substantially equal length referred to as “joints.” The joints, which generally include threaded connections, are typically joined end-to-end at the earth's surface (typically from a drilling rig) in order to form a substantially continuous “string” of pipe that reaches downward into a well. After the casing is installed within the well bore, the pipe is usually cemented in place.
During the pipe installation process, additional sections of pipe are added to the upper end of the pipe string at the rig in order to increase the overall length of the pipe string and its penetration depth in a well bore. The addition of pipe sections at the surface is repeated until a desired length of pipe is inserted into the well. The rate of assembly and installation of the casing can amount to many hours of total work time which, in turn, equates to higher costs. As such, time reduction in pipe string assembly and installation operations can result in significant cost reduction.
Conventional casing installation operations typically involve specialized crews and equipment mobilized to a well site for the specific purpose of assembling casing and installing such casing into a well. Recently, a method of running casing using a rig's top drive system, together with specialized casing running tools (RT's), has become increasingly popular. In many cases, casing can be run more efficiently and for less cost using an RT, compared to conventional casing crews and equipment, because RT's can be used to pick up and stab joints of casing and to provide torque to make up threaded casing connections. As a result, specialized casing tongs are frequently not needed, and fewer personnel are required on and around the rig floor during the casing running operations.
In most cases, a RT is connected immediately below a rig's top drive unit prior to commencement of casing operations. A single-joint elevator, supported by a RT, is typically used to lift individual joints of casing from a V-door or pipe rack into a derrick in vertical alignment over a well. The top drive and attached RT are lowered until the RT is proximate to the top of the new joint being added. The slips of the RT are set on the new joint of casing, and the top drive is actuated to apply the required torque (through the RT) to make up the casing to the upper end of the casing string previously installed in a well. At times, during the lowering of the pipe string into the well, the pipe string can be rotated and/or reciprocated using the RT to facilitate installation in the well.
In certain circumstances, it is beneficial for an RT to grip a pipe section internally (i.e., within the internal bore of such pipe), while in other circumstances it may be better to grip such pipe externally (i.e., on the outer surface of such pipe). However, because such functions generally require very different RT equipment configurations, most RT systems are designed for either internal gripping of pipe or external gripping of pipe, but cannot be converted from one method to the other. Further, existing RT systems generally provide for relatively low rotational rate (rpm), primarily due to limitations associated with hydraulic swivel seals.
In economic interest, the feed rate during the lowering of a pipe string into a well should be maximized, within the limits of safety considerations. Thus, there is a need for an RT that can pick up, assemble, rotate, and reciprocate casing or other pipe during installation operations, while having the ability to fill up fluids and compensate such casing or pipe during critical make up or break out procedures. The RT should allow for quick and efficient conversion between internal and external pipe gripping methods, while also permitting high rotational rates.